Multi-stage centrifugal pump or blower



June 5, 1956 A. BUCHI MULTI-STAGE CENTRIFUGAL PUMP OR BLOWER 3Sheets-Sheet 1 Filed March 17, 1953 Inventor- ALFRED BUCHI June 5, 1956A. BUCHI MULTI-STAGE CENTRIFUGAL PUMP OR BLOWER 3 Sheets-Sheet 2 FiledMarch 17, 1953 Inventor.- ALFRED BUCHI United States Patent MULTI-STAGECENTRIFUGAL PUMP 0R BLOWER Alfred Buchi, Winterthur, SwitzerlandApplication March 17, 1953, Serial No. 342,830

Claims priority, application Switzerland March 21, 1952 13 Claims. (Cl.103-108) The present invention relates to multi-stage con'trifugal pumpsor blowers and relates to the particular construction of one or moreguide device parts arranged in the direction of the flow of the pressuremedium to at least one rotor wheel and surrounding this at leastpartially, and of the reversing passages connected thereto. These partsdirect the pressure medium from one rotor wheel to the next.

The main object of the particular construction of such a guide deviceresides in so simplifying the production of the casing parts whichcontain the reversing passages and to render them so accessible that anaccurate finishing operation and also cleaning of the reversing passagesis rendered possible and facilitated. Further, by this construction theproduction of the casing parts can be carried out by casting, pressingand the like in an advantageous manner and with considerable accuracy.

The construction of a multi-stage centrifugal pump or blower accordingto the invention consists in that at least the stationary guide deviceparts of the separate stages of a multi-stage centrifugal pump or of ablower, surrounding the rotor wheels and conducting the pressure mediumto the succeeding rotor wheels, are constructed as parts separated inplanes normal to the axis of the pump and reversing passages conductingthe pressure medium from one stage to the next are constructed aspassages open in an axial direction, which in the assembled pump arecovered by separate annularcover plates.

In a preferred form of construction of the annular cover plates theseare provided internally with a bore, of which the wall coincides withthe outer limit of the next rotor wheel opening. The construction may besuch that at least one cover part projects with an annular projection onthe outer side into an annular offset and is so constructed andconnected to guide device parts that on the outside there is formed withthe projection a centring fitting and packing connection and 'on theinside, with projection of the cover plate, a packing relatively to thenext succeeding rotor wheel on its inlet side. The guide device parts,which can be separated from one another, of the separate stages mayadvantageously be held together in a cylindrical casing envelope. Inorder to keep frictional losses in the reversing passages as small aspossible, special precautions are taken; these passages may, forexample, have a continuously curved shape in the directionvof diffuserpassages in the guide device parts arranged directly in front thereof.For further reducing losses, the reversing passages may be so curved ina progressive and continuous manner, but differently at their inletportions from the direction from the diffuser passages at their innerportion in a direction towards the next rotor wheel, that both thewidths of the reversing passages transversely to the direction of flowand their radii of curvature, vary in such a manner that the ratio ofradius of curvature to 2 width of the reversing passages is as large aspossible and is never less than 1.5 1.

The through-flow cross-sectional areas of the reversing passages may befurther divided, in at least one of their curved parts, transversely tothe direction of flow of the pressure medium by guide blades extendingin an axial direction. The method of construction may be such thatagainst at least one outer part, containing the reversing passages,bears an internally and externally circular inner part arrangedco-axially to the pump axis and closes its cover part, this part is aguide passage body forming the continuation of the reversing passage tothe inlet port in the next rotor wheel and is fitted with rotor blades.The construction of the reversing passages may be such that these form,with their adjacent limiting walls extending in axial direction, anacute angle towards the interior. The points at which these limitingwalls meet to form the said angle may be contiguous with the guideblades which conduct the pressure medium into the inlet port of the nextrotor wheel. The point may, however, be also located opposite the inletport to the next rotor wheel. The through-flow cross-sectional areas ofthe reversing passages at the parts thereof curved in the direction offlow may be so sub-divided radially by axially extending annular guideblades, that the spacing of these guide blades transversely to thedirection of flow amongst themselves and relatively to the limitingwalls is determined by a predetermined constant ratio of the averageradii of curvature of the subdivided separated reversing guide passagesto the width thereof.

Several examples of construction of the subject of the invention areillustrated in the accompanying drawings wherein:

Fig. l is a longitudinal section of a first form of construction of theinvention through the axis of a multistage centrifugal blower on theline 1-1 of Fig. 2.

Fig. 2 is a cross section on the line II-II of Fig. 1.

Fig. 3 is a cross section on the line III-III of Fig. 1.

Fig. 4- is a longitudinal section of a second form of constructionthrough the axis of a multi-stage centrifugal blower on the line IV-IVof Fig. 5.

Fig. 5 is a cross section on the line V-V of Fig. 4.

In Fig. i, 1 indicates the rotor wheels of a 5-stage blower. These maybe of any construction. 2 is the common driving shaft to which the rotorwheels are keyed. 3 is a distance piece arranged between two rotorwheels. 4 and 5 are the stationary guide device parts surrounding therotor wheel of at least one stage and containing the guide passages forthe pressure medium. These blower parts are mounted in a casing cylinder7 with flanges 7a and 7b. The pressure medium inlet casing i342, 1312and pressure medium outlet casing 14 are so bolted to the flanges 70.and 7b that the guide device parts of each stage and the stages arepressed together. Each stage with the exception of the end stage isprovided with reversing passages 8, which conduct the pressure medium ofone stage to the rotor wheel of the succeeding stage.

The guide device parts 4 and 5, according to the invention, areconstructed as parts separated in a plane normal to the axis of thepump, Whilst the reversing passages are completely open towards one sidein the axial direction. Annular cover plates 10 are provided for thereversing passages 8. The inner bore of the plate 10 is indicated at 11.The outlet edge of the bore 11 coincides with the outer limit of therotor wheel inlet opening. The cover plate 10 is provided on its outerside in the axial direction with an annular projection 10a. The outerlimiting surface of the projection engages with a close and tightconnection with the guide device part 5. The projection 10a is providedon the inside towards the rotor Wheel with a labyrinth or similarpacking. The outer periphery of the plate 10 engages with an annulargroove 4a. This groove is formed by the guide device parts 4 and 5. Thecentring of the plate with the axis of the rotor wheel may be effectedby means of the groove 41: and the outer peripheral edge of the plate10, or also by means of the inner axial bore of the guide device part 5and the projection a of the plate 10. The packing rings are indicated at20.

The axial bore in the part 4 is provided opposite the distance piece 3with a labyrinth packing.

According to Fig. 2, as also according to Fig. 5, five guide passages 18are connected to a gap space 16 and collecting passages 17, by which thepressure medium flowing from the collecting passages 17 is firstconducted along straight line diffusers 18' extending tangentially tothe rotor wheel and transversely relatively to the blower axis. From thediffusers the conveying medium passes into diltuser passages 18connected tangentially to 18 and bent in the peripheral direction, whichare enlarged at least in the cross-sectional direction and so bent inthe axial direction, that they conduct the conveying material directlyinto the reversing passages 8 located laterally of the rotor wheel. Eachreversing passage is provided in the direction of the guide and diffuserassociated therewith with a continuously bent shape. The walls 8a and 8bof the reversing passages 8 are not only bent continuously, but thesewalls, determining the widths of the reversing passages, are provided inthe transverse direction to the flow of the pressure medium withcontinuously changing radii of curvature.

The ratio of these radii of curvature to the width of the reversingpassage is made as large as possible at the same points, namely, solarge that it is never less than 1.5 :1. As the reversing passagesbecome wider in the direction of flow, the radius of curvature of thewalls 8:: decreases in this direction. Guide blades are provided in thedirection of flow of the pressure medium, which divide the reversingpassages at least in one part of their bent portions transversely to theflow. The adjacent walls 81: and 8b of the reversing passage limtingwalls following one another in the direction of rotation, which extendin an axial direction, form at 80 (Fig. 2) an acute angle, whereupon thewalls 8a and 8b pass into the guide blades 6a.

Fig. 3 shows the construction of the annular space 14a connected to thelast stage and provided with the outflow nozzle 14b. The conveyingmedium is supplied through the inlet member 13b and the annular chamber13a to the rotor wheel 1 (Fig. 1). The construction of the collectingchamber connected to the last stage is not the subject of the presentinvention and may, as shown, or instead of being arranged laterally ofthe passages 18, be arranged, for example, vertically above the same.

According to another form of construction as shown in Fig. 4, the innerpart of a reversing passage is located in an axially located inner guidedevice part 6, and the larger outwardly connected reversing passage partis formed in a casing part 4 open on one side towards the next stage.The open part is covered by an annular plate 10 which extends up to theinterior of the guide device part 6. In the interiorly arrangedreversing passage parts 8 are provided the guide blades a (see also Fig.5). The guide part 5 is similarly constructed, as described inconnection with Fig. 1, whereas the part 4 is only provided for formingthe outer part of the reversing passages 3' and inwardly connected tothe part 6 which contains the inner part of the reversing passages. Onthe outside the part 6 is also provided with a circular surface whichforms tight and packing connections with the guide device parts 4', 5and the annular cover plate 10'. The part 6 contains the continuation ofthe outer reversing passage up to the inlet opening into the next rotorwheel. It is provided on the side of the next succeeding rotor wheel inaxial direction with a similar projection 10b to the inner part of thecover plate 10 shown in Fig. 1. This projection is here indicated by 6b,and its outer annular surface is located relatively to the part 5 in thesame manner as the projection 10b.

Annular guide blades 12 are provided in the curved part of the reversingpassages before the inflow of the pressure medium into the rotor wheels,said blades 12 extending in the axial direction and dividing these partsof the reversing passages in a radial direction. The spacing of theseguide blades relatively to one another and from the limiting walls isdetermined by a definite constant ratio of the central radii ofcurvature of the subdivided separate reversing passages to the widththereof. The plate 10' projects in a radial direction outwardly asdescribed in connection with Fig. 1 in respect of plate 10, into anannular groove, formed by the part 4 and 5. According to Fig. 5 thelimiting walls 8a and 8b of each two succeeding reversing passages areguided in the guide device part 6 up to the inlet opening 11a into therotor wheel of the succeeding stage, where they meet at 8c at an acuteangle, and are thus constructed as guide blades 6a. The point indicatedat in Fig. 2 corresponds in this case with the point indicated at 8c.This construction of the reversing passages can also be used withoutdifficulty also in the forms of construction shown in Fig. 1.

As shown in Figures 1 and 4, the inner parts of the reversingpassagesformed in Fig. l by the cover plate and the thereto opposed wallof part 4-deviate from their radial direction for a relatively shortdistance into a direction askew to the blower axis, thereby it ispossible to provide for a relatively greater radius of the reversingpassage portions that connect with the inlet port of the next rotorwheel.

What I claim is:

1. A multi-stage centrifugal pump or blower comprising a common shaft, aplurality of rotors fixed to said shaft, two separate housing partssurrounding each rotor for one pressure stage, one for the front orinlet side of the rotor and the other for the back side of the rotor,the inside surfaces of said two housing parts being set contiguouslybeside one another along a normal division plane, the inside of bothhousing parts together forming a stationary guide device having aplurality of separate peripheral guide ducts receiving the pressuremedium from the rotor, the discharge end of said guide ducts beingdeflected axially towards the following higher pressure stage, an equalnumber of secondary guide ducts on the axially outer side of said backside housing part, each of the secondary guide ducts being inregistering connection with said discharge end of the peripheral guideducts and being curved radially inwardly to thereby reverse the flow ofthe pressure medium in the peripheral guide ducts and to direct thepressure medium into the rotor inlet of the next following higher stage,said secondary or reversing guide ducts forming open channels in saidback side housing part mainly in the direction towards the rotor inletof the next following higher pressure stage, said channels being definedcircumferentially by axially extending division walls, an annular bodypressed against the free ends of said division walls, shoulder means onthe axially outside surface of the housing part of the next followingpressure stage bordering said annular body, the free ends of saiddivision walls lying at least in the radially outer portions of saidsecondary guide ducts in a plane normal to the rotor axis, said annularbody being constructed as an annular substantially fiat platesurrounding the inlet to the rotor of the next following higher pressurestage, and said shoulder means being disposed to substantially borderthe inner and outer perimeter of said front side housing part of thefollowing pressure stage.

2. A multi-stage centrifugal pump or blower according to claim 1,wherein the said annular body is provided on its inner surface with abore which registers with the outer boundary of the next rotor inletport.

3. A multi-stage centrifugal pump or blower according to claim 1,wherein the housing parts forming guide passages are held together in acylindrical casing envelope.

4. A multi-stage centrifugal pump or blower according to claim 3,wherein said annular body projects on thebutside into an annular recessand is so constructed and connected to the other parts forming guidepassages that on the outside a centering and packing connection isformed and the inner side of each annular body is formed as a packingrelative to the next succeeding rotor on its inlet side.

5. A multi-stage centrifugal pump or blower according to claim 1,wherein the reversing passages have a continuously curved shape in thedirection of the diffused passages in the parts forming guide passages.

6. A multi-stage centrifugal pump or blower according to claim 1,wherein the reversing passages are curved so that their widthstransverse to the direction of flow and their radii of curvature vary insuch manner that at same points the ratio of the radius of curvature tothe width of the reversing passages is as large as possible but isnowhere smaller than 1.5 :1.

7. A multi-stage centrifugal pump or blower according to claim 1,wherein the through-flow cross section of the reversing passages and atleast in a part of their curved portions is sub-divided transversely tothe direction of flow of the pressure medium by guide blades extendingin axial direction.

8. A multi-stage centrifugal pump or blower according to claim 1,wherein the limiting walls of the reversing passages extending in asubstantially axial direction and being located side by side form anacute angle toward the inside, and the points at which the limitingwalls meet to form the said angle are contiguous with guide blades whichconduct the pressure medium into the inlet port of the next rotor.

9. A multi-stage centrifugal pump or blower according to claim 1,wherein the point at which the axially extending limiting walls of thereversing passage run into one another is located substantially oppositethe inlet port to the next rotor.

10. A multi-stage centrifugal pump or blower according to claim 1,wherein the through flow cross-section of the reversing passages atleast at their curved portions is so sub-divided in the direction offlow by axially extending annular guide blades that the spacing of theseguide blades transversely to the direction of flow between themselvesand relatively to the limiting walls is determined by a definiteconstant ratio of the average radii of curvature of the sub-dividedseparate reversing guide passages relatively to the widths thereof.

11. A multi-stage centrifugal pump or blower according to claim 1,wherein the reversing passages at their inner portions deviate fromtheir radial direction for a relatively short distance into a directionaskew to the blower axis, and turns tangentially to said axis at arelatively great radius towards and into the inlet port of the nextrotor wheel.

12. A multi-stage centrifugal pump or blower according to claim 1,wherein on an outer part containing the reversing passages an innerguide passage body is arranged coaxially to the axis of the pump, saidbody being circular inside and outside so as to connect with the annularbody for the reversing passages in said outer part and being formed withcontinuing portions to the inlet port in the next rotor wheel of thereversing passages in said outer part.

13. A multi-stage centrifugal pump or blower according to claim 12,wherein said inner guide passage body is provided with guide blades inthe continuing portions of said reversing passages.

References Cited in the file of this patent UNITED STATES PATENTS1,142,882 Johnson June 15, 1915 2,483,643 Karrer Oct. 4, 1948 2,596,646Buchi May 13, 1952 2,596,647 Buchi May 13, 1952 FOREIGN PATENTS 342,065Great Britain Ian. 29, 1931

